1. Field of the Invention
This invention relates to a lock device, and particularly to a picklock-proof key slot for a lock device and a key thereof.
2. Description of the Prior Art
In the conventional lock devices, the lock-up relation between the outer lock cylinder and the inner lock cylinder is different because of the shapes of the keys being different; such lock devices may be classified as spiral lock, tube lock, hub-shaped lock, straight slot lock and flat plate lock; in the flat-plate lock the inner lock cylinder is furnished with a key hole, which designed at an angle of 90 degrees to the tumbler grooves. The flat surface of the key is furnished with tumbler grooves; the aforesaid lock structure is deemed the most difficult lock device to be picked because of the key slot of such lock device is set at an angle of 90 degrees from the inner tumbler grooves; the flat plate of the key has a thickness of 3.0 mm; if a master key is plugged into the key slot to pick, the master key is unable to push the lower tumblers to move up and down on a straight line; it can only move and push the lower tumblers at an incorrect position, i.e., along a straight line, and then the lock device can be unlocked.
In the conventional technology of lock device, the manufacturing precision is unable to achieve the effectiveness as desired as a matter of convenience during manufacturing. The lock device comprises an outer lock cylinder and an inner lock cylinder; between the upper tumblers and the lower lock cylinders, there is a curved unlocking tangent; the lock device can be picked easily with a master key because of the design of the key slot in the inner lock cylinder. In a straight slot lock, the width of the key slot is 2.0 mm; the diameter of a master key is ranging from 0.8 mm to 1.0 mm; the motion space for the lower tumblers in the key slot is ranging from 5.0 mm to 6.0 mm, while the bent front end of the master key is ranging from 2.5 mm to 3.0 mm; the inner lock cylinder is furnished with a space having a height of 3.0 mm for applying force. The slot of such lock device has a shape, which enables a master key to plug in and to move back and forth so as to pick the tumblers and to unlock the lock device.
The prime object of the present invention is to provide a lock device, in which the center line between the lock casing and the rotary cylinder is furnished with a plurality of tumblers arranged regularly; a key slot is furnished under the tumbler grooves of the rotary cylinder, and it is two U-shaped key slots. The center of the U-shaped key slot has a salient plate, of which both sides are furnished with symmetrical guide slots; the space between the two guide slots are used for receiving the curve surface of the lower tumblers. Since the space is quite narrow and the contact point is a curved one, a very thin master key plugged in will be very difficult to push the lower tumblers as a result of the sloping contact point; the master key might be damaged or broken.
Another object of the present invention is to provide a lock device, in which the key slot of the rotary cylinder is a U-shaped hole, which includes two symmetrical guide slots and a bottom slot; the bottom surface thereof has a height of 1.0 mm only, which can prevent a master key from plugging into the curve center of the lower tumbler to pick the lock device.
Still another object of the present invention is to provide a lock device, in which the key slot of the rotary cylinder is a U-shaped hole, which includes two symmetrical guide slots and a bottom slot; the width of the two symmetrical guide slots is merely 1.0 mm, and the height thereof is less than 2.5 mm so as to limit the thickness and the height of a master key, and to reduce the space for the master key to push the lower tumbler to move.
A further object of the present invention is to provide a lock device, in which the key slot includes two symmetrical guide slots; the lower tumblers loaded in the tumbler grooves have curve surfaces on the bottoms thereof loaded in the guide slots respectively; since the master key is usually made of a saw blade, which is to be used together with an electro-motive tool; in that case, the master key is subject to breaking as a result of heavy resistance; the master key may be made of a steel wire, but the master key is susceptible to being bent upon the end thereof applied with heavy resistance.
A still further object of the present invention is to provide a lock device, in which the key to be plugged into the key slot of the rotary cylinder has symmetrical U-shaped key slot. The guide slot between the symmetrical guide plates is directed along the salient plate between the symmetrical guide slots; the lower tumblers are in the center of the salient plate. The top surface of the two symmetrical guide plates is drilled with a plurality of unlock-tumbler holes having different depth so as to push the plural lower tumblers to move upwards, and to have the top surface of all the lower tumblers reached the rotary tangent between the lock casing and the rotary cylinder; then, the key can drive the rotary cylinder to the unlock position.
Yet another object of the present invention is to provide a lock device, in which key plugged in the key slot of the rotary cylinder has two symmetrical guide plates, between which a guide slot is furnished; the unlock-tumbler holes for pushing the lower tumblers are furnished inside the two symmetrical guide plates; the unlock-tumbler holes are designed into a shape or a tapered surface to fit the curve surface of every lower tumbler; the symmetrical guide plates are divided into several equal sections. When the two symmetrical guide plates are drilled with unlock-tumbler holes, the depth thereof will be varied accordingly; likewise, the length of every lower tumbler will also be varied so as to have a smaller space to prevent a master key from pushing the lower tumblers to move, i.e., the master key will be unable to push all the lower tumblers up to the rotary tangent between the lock casing and the rotary cylinder; in other words, the master key is never able to unlock the lock device.